多年生禾豆混植草青貯發酵探討

Silage fermentation characteristic of perennial grass-legume mixture

陳嘉昇(Chia-Sheng Chen) ； 王紓愍(Su-Min Wang) ； 游翠凰(Tsui-Huang Yu)

《畜產研究》 50卷1期 (2017/03) Pp. 52-61

摘要

禾豆混植草地可以提升牧草營養價值、平衡土壤養分利用，然而在臺灣的氣候條件下，穩定的禾本科生產已屬不易，調製禾豆混植乾草的難度更高，青貯調製是一個可能的解決方法。本研究以三組試驗探討青貯變動與影響因素：試驗一材料含2種禾本科及2種豆科，禾本科所佔比例自30%至100%。未經萎凋，青貯8週後，pH介於4.25－4.85，總產酸量3.0－6.4%（dry base），乳酸與乳／乙酸比（lactic acid/acetic acid ratio）低，且均有丁酸（butyric acid）產生，表示禾豆混植材料未降低含水率下無法獲得良好結果，乳酸菌（lactic acid bacteria）接種亦無法產生效益。試驗二以萎凋至乾物率38%的盤固草與苜蓿混植為材料，比較菌種與4、8、12週的青貯結果，總產酸雖低於試驗一，但各揮發性脂肪酸含量比例佳，乙酸、丁酸降低，乳酸乙酸比提升，除對照組外，青貯評分均達優良等級。各接種劑均有助於乳酸的快速生成，而菌種之間的產酸反應有別。不同時間開封的比較方面，12週時總酸量約為4週時的兩倍；4週時對照組的pH顯著高於其他接種處理，8週時則與其他處理差距拉近，表示在相對適宜的青貯條件下不接種者雖可獲良好品質評分，但充分產酸需時較長。試驗三測試小型生產規模（桶式與小香腸）調製。在不嚴格的無氧狀況下，接種與未接種者之間的差距放大，接種者發酵品質達優良等級；未接種者pH降幅小、乳酸乙酸比低，且有高量的丁酸生成，屬於失敗的青貯等級。由本研究結果，含水率是禾豆混植草青貯的關鍵因素，而在未能完全排除空氣的裝填操作之下，接種菌劑可提升及穩定青貯發酵，而接種與較適含水率範圍的配合宜進一步探討。

關鍵字

禾豆混植 ； 接種劑 ； 青貯

並列摘要

Grass-legume mixture has the function of elevating nutritional value of forage and balancing soil nutrient. Owing to the humid climate of Taiwan, hay drying of grass is not easy, hay making of grass-legume is even more difficulty. Ensiling will be a feasible alternative for mixture production. Three experiments were conducted in this research to investigate the fermentation characteristics of grass-legume mixture and their affecting factors. Two grasses and two legumes were included in experiment I and their grass percentage ranged from 30% to 100%. After 8 weeks ensiling of the un-wilted forages, the pH were 4.25-4.85, total acids were 3.0-6.4% (dry base) and all were low in lactic acid and low lactic acid/acetic acid ratio and high butyric acidyielding. It indicated that good fermentation can't be attained under high moisture condition even inoculation were applied. In experiment II, silages were made of pangola-alfalfa mixture wilted to 38% DM (dry matter) with or without inoculation and were assayed at 4, 8 and 12 weeks. Silages of experiment II showed lower total acids, lower acetic acid and butyric acid but higher lactic acid/acetic acid ratio as compared to those in experiment I. All treatments in experiment II got excellent score except that without inoculation. All inoculants used in this experiment were helpful to lactic acid synthesis, but had different effects on fermentation product. Silages without inoculation were higher in pH than others at 4 weeks storage, while the differences between them were closer after 8 weeks. It indicated that though good fermentation could be achieved without inoculation under proper condition, but longer time was required for fermentation. In experiment III, grass-legume mixtures were filled into barrel and sausage bag with or without inoculation. The results showed that divergence effects of inoculation or not were magnified under the conditions that air can't be exclusively repelled. Silage with inoculation were excellent in grade, while that of without inoculation were failed in both types of ensiling. It is concluded that moisture is the key factor to grass-legume ensiling. In practical operation, which rigorous anaerobic condition is hard to reach, inoculation can promote and stabilize fermentation quality. The endurable ranges of moisture that act in concert with inoculation for good fermentation need further study.

並列關鍵字

Grass-legume mixture ； Inoculant ； Silage